As integrated circuits become more complex, the circuit density of the chips increases. One square centimeter chips can contain millions of separate electronic components. Increased heat removal demands have been an on-going problem. Traditional cooling methods for thermal control such as forced gas and liquid convection have been replaced by direct liquid impingement boiling heat transfer. Liquid impingement with phase-change at a heated chip surface offers the promise of providing chip cooling capability in excess of 100 W/cm.sup.2.
The means of providing liquid impingement on the chip is often in the form of single or multiple liquid jets, or in the form of a liquid spray with many small droplets. With many chips packaged closely together and operating at high heat fluxes the vapor generated mixes with the exhaust liquid creating a two-phase mixture of liquid and vapor. As the void fraction or the ratio of local vapor volume to total local flow volume increases, instabilities tend to result in disruptions in coolant flow to the chip. Similarly, if the vapor in the exhaust liquid is not condensed before returning to the pump the flow delivery capability of the pump will be degraded and the pump could suffer physical damage.